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The birds had starved, apparently due to lack of food in abnormally warm ocean water

(CNN)As he walked on a beach in the western Prince William Sound town of Whittier, seabird biologist David Irons was startled when he saw hundreds of white lumps on the black rock beach.

They were dead seabirds, in what he would discover were likely record numbers, a sign the ecosystem was being troubled by abnormally warm ocean water.

The dead birds, common murres that had starved, were lined up and left where the tide had dropped them on the shore.

"We have never found close to 8,000 birds on a 1-mile long beach before," Irons said of his early January discovery. "It is an order of magnitude larger than any records that I am aware of."

Biologists like Tamara Zeller have been boating around Prince William Sound scanning the beaches for dead and sickly murres. They also count the birds floating in the water, she told CNN affiliate KTVA.

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They cannot stop at every beach so they estimate the disturbing total of birds from the ship. When they are able to get to shore, the toll is always much higher.

At Whittier, one day about two weeks ago, she counted 98 of the black and white birds while on the water. On shore she saw 284. The day's total for January 7 was 3,000.

The birds, all of a species known as the common murre, appear to have starved to death, federal wildlife officials say.

Heather Renner, a supervisory biologist at the Alaska Maritime National Wildlife Refuge, said the Whittier die-off is part of a much larger event that started in August.

Renner estimates that 100,000 common murres have died.

"It's hard to know how many birds have died because Alaska is so big, and there are so many remote areas," Renner said.

The vast majority of the bird deaths are due to starvation. Tests on 100 carcasses revealed almost all the murres were emaciated, and the culprit is likely their lack of a good food supply.

"The fish that they eat tend to have a narrow band of water temperatures they can live in," Irons said. "If the temperature gets too warm or too cold the fish disappear."

And there's plenty of warm water off Alaska's coast right now. Since 2013, an expanse of seawater that's 2 to 7 degrees Fahrenheit above average has stretched from Asia to North America. Scientists have dubbed it "the blob," and they're studying it closely for its effect on wildlife.

According to the U.S. Fish & Wildlife Service, murres usually spend the winter offshore, diving into the water for fish, crustaceans and mollusks. The average adult murre weighs 2 pounds and eats up to 30% of its body weight per day.

They typically dive as deep as 250 feet, but if they need to, almost 600 feet is possible. Their short wings make them excellent swimmers.

The 8,000 dead common murres that Irons observed doesn't put a dent in the overall population. Neither does Renner's estimation of 100,000 bird deaths. There are approximately 2.8 million murres in Alaska.

Their deaths give clues to a larger picture, Irons said.

"Seabird biologists say seabirds are indicators of the health of the ecosystem. Now they're dying and that is telling us something. We should be aware of that. If we don't record they're dying it goes unnoticed," Irons told KTVA.

The scientists also say that die-offs aren't uncommon. One in 1993 was estimated at 100,000 murres. There was one in 1997 -- during an El Niño -- that affected several types of birds. At that time scientists also focused on warm water and the lack of food.

And almost 190,000 murres perished after the Exxon Valdez crashed in the sound in 1989, spilling more than 1 million gallons of oil.

But Irons and Renner say this die-off is different in its scope and the persistence of the warm water blob that may have caused it.

"Scientists tend to get blasé about (die-offs) but this is bigger than I've ever seen," Irons told KTVA.

Renner agreed.

"This is probably one of the larger events and going over a longer period of time and a bigger geographical area," Renner said.

Murres aren't just being found on shorelines. They also have been picked up as far inland as Denali State Park, CNN affiliate KTUU reported.

Being on land means trouble for murres, whose bodies are designed to take off from water. The inland murres are grounded and needed to be taken back to the ocean. Before that they are taken to a rehab facility.

At the Bird Treatment and Learning Center in Anchorage, staffers usually see a few sick or starving murres each year. So far this season more than 225 have been brought in.